Implanted spacer approaches for pelvic radiation therapy

Introduction: Recent clinical advances in radiation therapy have aimed to improve the therapeutic ratio through shortening the treatment duration through increasing the biologically effective dose (either through dose escalation or hypofractionation). However, despite using advanced techniques such as intensity modulated radiation therapy (IMRT) and image-guidance methods, dose escalation can be limited by its resultant gastrointestinal toxicity. In an effort to reduce rectal toxicity, biodegradable spacer materials and implantable balloons have been injected into the prostate-rectal space to increase the separation between the rectum and prostate thereby reducing rectal irradiation. Areas covered: The purpose of this review is to describe the commercially available rectal spacers in pelvic radiation therapy, including prostate cancer and gynecologic malignancies, and to discuss the application, dosimetric effects, and reported clinical outcomes to date. Expert commentary: Several groups have reported significantly reduced rectal doses and decreased rectal toxicity with prostate-rectal spacers, and additional evidence continues to emerge to support this promising approach.